Process of assembling solid electrolytic capacitors using vibration step with both low and high frequency components

ABSTRACT

A solder preform slug and a processed anode are placed into a can. A glass end seal and an outer solder preform O-ring are placed on a lead extending from the anode. The assembled components are heated to the melting temperature of the solder preforms. The can is vibrated by applying high frequency vibrations to a bar supporting the can. The bar has a natural low frequency of vibration such that both the high frequency vibrations and the low frequency vibrations are applied to the can. The low frequency vibrations settle the anode into the can and release gases which are produced from rosin. The high frequency components produce rotation of the can which aids in the sealing of the end seal by the solder preform O-rings.

Unite States atent McClamrock [451 Sept. 12, 1972 Inventor: Grady L.McClamrock, Mocksville,

Assignee: Western Electric Company, Incorporated, New York, NY.

Filed: on. 2, 1970 Appl. No.: 77,488

US. Cl. ..29/570, 29/203 J Int. Cl. ..BOlj 17/00, H01 g 13/00 Field ofSearch ..29/570, 589, 203 P, 203 S, 29/203 .1, 500, 471, DIG. 46;317/230;

References Cited UNITED STATES PATENTS Fournier ..29/570 Felker et a1..29/589 X Oburt ..219/9.5

l /Iii llll Ill Ill llll:

3,005,257 10/1961 Fox ..29/589 3,284,257 11/1966 Soloff et all 156/733,474,523 l0/1969 Musso et al ..29/473.5

Primary ExaminerJohn R Campbell Assistant Examiner-D. M. HeistAtt0rneyW. M. Kain, R. P. Miller and W. L. Williamson [57] ABSTRACT Asolder preform slug and a processed anode are placed into a can. A glassend seal and an outer solder preform O-ring are placed on a leadextending from the anode. The assembled components are heated to themelting temperature of the solder preforms. The

can is vibrated by applying high frequency vibrations to abar supportingthe can. The bar has a natural low frequency of vibration such that boththe high frequency vibrations and the low frequency vibrations areapplied to the can. The low frequency vibrations settle the anode intothe can and release gases which are produced from rosin. The highfrequency components produce rotation of the can which aids in thesealing of the end sea] by the solder preform O-rings.

12 Claims, 5 Drawing Figures 5 2/ I I I g g g l A? l Ii 27 Iii "ll'lPROCESS OF ASSEMBLING SOLID ELECTROLYTIC CAPACITORS USING VIBRATION STEPWITH BOTH LOW AND HIGH FREQUENCY COMPONENTS BACKGROUND OF THEINVENTION 1. Field of the Invention A. solid electrolytic capacitor,such as a tantalum capacitor, is formed by (1) sintering finely dividedvalve metal, such as tantalum, into a porous anode mounted on a lead,(2) anodizing the porous anode to form a dielectric oxide layer, such astantalum pentoxide, (3) coating the anodized anode with a layer ofmanganese dioxide, (4) applying a coating of graphite, (5) applying acoating of finely divided silver, (6) dipping the coated anode into asolder bath, and (7) attaching the processed solder coated anode to acan with a lead extending therefrom. This invention is particularlyconcerned with the last step of attaching the processed anode to thecan.

2. Prior Art In the prior art, the processed anode along with a solderpreform slug are placed in a can. Also, a glass end seal and an outersolder preform O-ring are placed over the lead extending from theprocessed anode. The solder preforms have a suitable rosin coating. Theassembled components are then heated to the melting temperature of thesolder preform to connect the processed anode to the can and to seal theend seal to the can and the lead. However, gases formed by the rosin orreactions therewith often times prevent the anode from settling into thebottom ofv the can and prevent the end seal from seating on the open endof the can. While it has generally been known that vibrations in theultrasonic range can be used to weld or aid in the forming ofa bondbetween two metals, the use of ultrasonic vibrations has beenunsuccessful in overcoming the problems of settling the anode in the canor making a good seal on the end seal.

SUMMARY OF THE INVENTION An object of the invention is a new andimproved process for assembling processed capacitor anodes into cans.

Another object of the invention is the use of selected frequencyvibrations to aid in the assembly of a processed anode in a can.

In accordance with these and other objects, a process for assembling aprocessed capacitor anode in a can utilizes the steps of placing asolder preform slug and the anode in the can; heating the anode, can andsolder to a temperature above the melting point of the solder; andvibrating the can with a frequency having a low component between 100and 1,000 cycles per second and a high component between 3,000 and10,000 cycles per second.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an assembly drawing of a dryelectrolytic capacitor;

FIG. 2 shows a fixture for holding the capacitors while they are heatedand vibrated;

FIG. 3 shows a waveform of the vibrations applied to a carrier bar ofthe apparatus shown in FIG. 2;

FIG. 4 shows a waveform of the vibrations on the ends of the bar; and

FIG. 5 shows a waveform of the vibrations applied by the carrier bar tothe capacitor assembly.

I DETAILED DESCRIPTION Referring to FIG. 1 there is shown a capacitorassembly wherein a processed anode 10 is assembled into a can 11 alongwith a solder preform slug 12. A glass end seal 15 is placed on the lead16 extending from the processed anode 10. The end seal 15 is designed tofit in a groove formed in the upper inner edge of the can 11. An outersolder preform O-ring 17 is placed over the lead l6-on top of the endseal 15. The capacitor assembly is heated above the melting point of thesolder and vibrations having both high frequency and low frequencycomponents are applied to the can 11 to attach the processed anode 10 tothe can and to seal the end seal 15 to the can 11. Subsequently, thecapacitor assembly may be evacuated and filled with a specialatmosphere, such as dry air or an inert gas. Then the end seal 15 issealed to the lead 16 by an operator applying heat and solder to thelead 16 where it extends from the end seal 15. Alternately, an innerO-ring may be placed over the lead 16 prior to heating and vibrating thecapacitor assembly such that the lead 16 is sealed in the end seal 15 atthe same time the end seal 15 is sealed to the can 11.

Referring now to FIG. 2, there is shown an apparatus for heating andvibrating a plurality of assembled capacitors. A plurality of the cans1l-ll are placed on a bar 20 with welded leads 1313 extending from thecans 11-11 through apertures in the bar 20. The bar 20 is supported atits two ends on respective arms 21 and 22 which are attached torespective electromagnetic vibrators 23 and 24. The electromagneticvibrators 23 and 24 are supported by supports 25 and '26 mounted on atable top 27. An induction heating coil 28 suitably supported on thetable top 27 surrounds the cans l1-ll to heat the assembled units to themelting temperature of the solder.

The bar 20 has a suitable mass and length to have a natural frequencygenerally within the range of to 1,000 cycles persecond. Preferably thenatural frequency is from 200 to 400 cycles per second. The vibrators 23and 24 are connected in parallel to a power generator (not shown) whichexcites them at a frequency which is generally in a range of from 3,000to 10,000 cycles per second, and preferably in a range of 7,000 to 8,000cycles per second. The higher frequency applied by the vibrators 23 and24 to the bar 20 excites the bar into also producing vibrations of a lowfrequency which is the natural vibrating frequency of the bar. The lowfrequency vibrations of the bar 20 cause the anodes 1010 to settle tothe bottom of the cans 1 l1l and forces the gases formed from the rosinreacting within the cans 11-1l to escape past the sides of the anodesand out the end seal. The high frequency vibrations produce a rotativemotion of the cans 11- 11 which aids the settling of the end seals 15into the groove in the top of the can 11. Also, the rotative motion bycentrifugal force causes the molten outer solder preform O-ring to flowoutwardly into contact with the can 11 to insure an even solder bondaround the upper edge of the can 11 to seal the can. Experimentationwith different vibrators and different size and shapes of bars indicatethat this rotative motion is a natural phenomenon or thatelectromagnetic vibrators arcomponent of vibration to the bar 20. Onevibrator used by the inventor is model no. V-2-A sold by Syntron ofHomer City, Pennsylvania.

Referring to FIG. 3 the waveform 30 shows the high frequency vibrationsproduced by the vibrators 23 and 24. The only measurable vibrationproduced by the vibrators 23 and 24 is the high frequency vibration.Referring to FIG. 4 the waveform 28 shows the vibrations of the ends ofthe carrier bar 20. Referring to FIG. 5 the waveform 29 shows thevibrations applied to the cans 11. The vibrations applied to the cans 11have both the high frequency component and the low frequency component.The solder used may be selected from many acceptable solders, such astin-lead solders or tin-antimony solders.

It is to be understood that the above-described embodiment of theinvention is simply illustrative of the invention and that manyembodiments can be devised without departing from the scope and spiritof the invention.

What is claimed is:

l. A process of assembling a capacitor anode in a can comprising:

placing a solder preform and the anode in the can;

heating the anode, can and solder preform to a temperature above themelting point of the solder preform; and

vibrating the can with a vibration having a low frequency componentbetween 100 and 1,000 cycles per second and a high frequency componentbetween 3,000 and 10,000 cycles per second.

2. A process as defined in claim 1 wherein the frequency of vibration ofthe can has a low component between 200 and 400 cycles per second and ahigh component between 7,000 and 8,000 cycles per second.

3. A process as defined in claim 1 wherein rotated by the vibrations.

4. A process as defined in claim 2 wherein the can is rotated byvibrations.

the can is 5. A process as defined in claim 3 wherein an end seal and asolder O-ring are placed over a lead extending from the anode prior toheating and vibrating.

6. A process as defined in claim 4 wherein an end seal and a solderO-ring are placed over a lead extending from the anode prior to heatingand vibrating.

7. A process of assembling a plurality of capacitor anodes into aplurality of cans, one can for each anode comprising:

placing the plurality of cans into a plurality of recesses in a holdingmember which'has a natural frequency of vibration between and 1,000cycles per second;

placing a plurality of solder preforms into the plurality of cans, onepreform in each can;

placing the plurality of anodes into the plurality of 7 cans, one anodein each can; and

exciting the holding member by a vibration having a frequency componentbetween 3,000 and 10,000 cycles per second to vibrate the cans with botha low frequency component between 100 and 1,000 cycles per second and ahigh frequency component between 3,000 and 10,000 cycles per 8. i gr ofess as defined in claim 7 wherein the holding member has a naturalfrequency of vibration between 200 and 400 cycles per second and theholding member is excited by a frequency between 7,000 and 8,000 cyclesper second.

9. A process as defined in claim 7 wherein the cans are rotated.

10. A process as defined in claim 8 wherein the cans are rotated.

11. A process as defined in claim 9 wherein an end seal and a solderO-ring are placed over a lead extending from each of the plurality ofanodes prior to heating and vibrating.

12. A process as defined in claim 10 wherein an end seal and a solderO-ring are placed over a lead extending from each of the plurality ofanodes prior to heating and vibrating.

2. A process as defined in claim 1 wherein the frequency of vibration ofthe can has a low component between 200 and 400 cycles per second and ahigh component between 7,000 and 8,000 cycles per second.
 3. A processas defined in claim 1 wherein the can is rotated by the vibrations.
 4. Aprocess as defined in claim 2 wherein the can is rotated by vibrations.5. A process as defined in claim 3 wherein an end seal and a solderO-ring are placed over a lead extending from the anode prior to heatingand vibrating.
 6. A process as defined in claim 4 wherein an end sealand a solder O-ring are placed over a lead extending from the anodeprior to heating and vibrating.
 7. A process of assembling a pluralityof capacitor anodes into a plurality of cans, one can for each anodecomprising: placing the plurality of cans into a plurality of recessesin a holding member which has a natural frequency of vibration between100 and 1,000 cycles per second; placing a plurality of solder preformsinto the plurality of cans, one preform in each can; placing theplurality of anodes into the plurality of cans, one anode in each can;and exciting the holding member by a vibration having a frequencycomponent between 3,000 and 10,000 cycles per second to vibrate the canswith both a low frequency component between 100 and 1, 000 cycles persecond and a high frequency component between 3, 000 and 10,000 cyclesper second.
 8. A process as defined in claim 7 wherein the holdingmember has a natural frequency of vibration between 200 and 400 cyclesper second and the holding member is excited by a frequency between7,000 and 8,000 cycles per second.
 9. A process as defined in claim 7wherein the cans are rotated.
 10. A process as defined in claim 8wherein the cans are rotated.
 11. A process as defined in claim 9wherein an end seal and a solder O-ring are placed over a lead extendingfrom each of the plurality of anodes prior to heating and vibrating. 12.A process as defined in claim 10 wherein an end seal and a solder O-ringare placed over a lead extending from each of the plurality of anodesprior to heating and vibrating.